1. Field of the Invention
The present invention relates to an X-ray diffraction apparatus and X-ray diffraction measurement method based on X-ray topography.
2. Description of the Related Art
X-ray topography has been known as one of X-ray diffraction measurement methods. X-ray topography is a measurement method devised so that a wide area of a sample is irradiated with X-rays, and the diffracted rays exiting the sample are detected in a plane (that is, in two dimensions) by an X-ray detector. Specifically, X-ray topography is a method in which diffracted rays that have exited from a planar region of a sample are provided with a spatial geometric correspondence and captured as a planar X-ray diffraction image. The planar X-ray diffraction image is called an X-ray topograph.
The form characteristics that appear in an X-ray topograph typically represent the compositional characteristics of an object. For example, lattice defects and lattice distortion in a single crystal appear as changes in the X-ray intensity in an X-ray topograph. For this reason, X-ray topography, which is a measuring method for obtaining an X-ray topograph, is at present widely used as a method for assessing the integrity of crystals in single crystal materials such as the Si (silicon) substrates in semiconductor devices.
There are also X-ray diffraction measurement methods in which a very small region of a sample is irradiated with a very thin X-ray, and a diverse range of measurements is performed on the very small region. Examples of such measurement methods include qualitative analysis, rocking curve measurement, reflectometry, reciprocal lattice mapping, in-plane measurement, and the like.
In conventional practice, method is used for evaluating the crystallinity of a single crystal in which X-ray topography and rocking curve measurement are performed using the same X-ray measuring device (for example, see patent reference 1). According to the evaluation method, a single crystal is examined for the presence of crystal defects by an X-ray topograph determined by X-ray topography, rocking curve measurement is performed only in the vicinity of the discovered defects, and the crystal defects are quantitatively measured. According to this evaluation method, the measurement time needed for the rocking curve measurement is considerably reduced in comparison with a case in which rocking curve measurement is performed over a wide area of a sample.
In conventional practice, X-ray single crystal evaluation devices are also used in which X-ray topography and X-ray diffraction measurement are performed selectively by switching the positions of appropriate optical elements in a single X-ray diffraction measuring device. The X-ray topography may be Lang method, section topography, surface reflection topography, reflection topography with a crystal monochromator, or the like, and the X-ray diffraction measurement performed in a limited field of measurement may be diffracted X-ray intensity absolute measurement, rocking curve measurement, diffraction profiling with a set analyzer crystal, or the like (for example, see patent reference 2).